#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<int, int>;
#define rep(i, a, b) for (int i = (a); i <= (b); i++)
#define per(i, a, b) for (int i = (a); i >= (b); i--)
#define endl '\n'
const int N = 1e5 + 5;

int n, c;
int x[N];
bool check(int d) {
  int pre = x[1], cnt = 1;
  rep(i, 2, n) {
    if (pre + d <= x[i]) {
      cnt++;
      pre = x[i];
    }
  }
  return cnt >= c;
}
int main() {
  ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
  cin >> n >> c;
  rep(i, 1, n) cin >> x[i];
  sort(x + 1, x + n + 1);
  int l = 1, r = 1e9;
  while (l <= r) {
    int mid = (l + r) >> 1;
    if (check(mid))
      l = mid + 1;
    else
      r = mid - 1;
  }
  cout << r;
  return 0;
}